Add example of edge list-colouring

Makefile

@@ -1,4 +1,7 @@
-png: png/petersen-node.png
+png: png/petersen-edge.png png/petersen-node.png
+
+png/petersen-edge.png: src/petersen-edge.py
+	poetry run python $<
 
 png/petersen-node.png: src/petersen-node.py
 	poetry run python $<

README.md

@@ -6,3 +6,7 @@ Constraint-based list-colouring in Python with vizing.
 
 ![](png/petersen-node.png)
 
+## Edge list-colouring
+
+![](png/petersen-edge.png)
+

pyproject.toml

@@ -5,6 +5,7 @@ description = "Constraint-based list-colouring in Python with vizing."
 authors = ["Matthew Henderson <[email protected]>"]
 license = "MIT"
 readme = "README.md"
+package-mode = false
 
 [tool.poetry.dependencies]
 python = "^3.12"

src/petersen-edge.py

@@ -0,0 +1,31 @@
+import listcolouring as lc
+import matplotlib.pyplot as plt
+import matplotlib.patches as mpatches
+import networkx as nx
+import vizing as vz
+
+G = nx.petersen_graph()
+
+G = lc.list_init(G, range(0, 10), 3, 0)
+
+G = vz.edge_list_colouring_solution(G)
+
+G_layout = nx.shell_layout(G, nlist = [range(5, 10), range(5)], rotate = 0.)
+edge_colours = nx.get_edge_attributes(G,'colour').values()
+
+nx.draw(G,
+                pos = G_layout,
+         edge_color = edge_colours,
+        with_labels = False,
+          edge_cmap = plt.cm.tab10,
+              width = 5,
+          node_size = 150,
+         node_color = 'black')
+
+edge_labels = dict([((n1, n2), str(d['colour']) + ': ' + str(sorted(d['permissible']))) for n1, n2, d in G.edges(data = True)])
+X = nx.draw_networkx_edge_labels(G, pos = G_layout, edge_labels = edge_labels, font_size = 6)
+
+patches = [mpatches.Patch(color = plt.cm.tab10(i), label = f'{i}') for i in edge_colours]
+plt.legend(handles = patches, title = "Colours", bbox_to_anchor = (1, 1))
+
+plt.savefig("png/petersen-edge.png", format = "PNG")

src/petersen-node.py

@@ -1,16 +1,12 @@
+import listcolouring as lc
 import networkx as nx
 import matplotlib.pyplot as plt
 import matplotlib.patches as mpatches
-
-import listcolouring
-from listcolouring import list_init_node
-
-import vizing
-from vizing import list_colouring_solution
+import vizing as vz
 
 G = nx.petersen_graph()
-G = list_init_node(G, range(1, 10), 3, 0)
-G = list_colouring_solution(G)
+G = lc.list_init_node(G, range(1, 10), 3, 0)
+G = vz.node_list_colouring_solution(G)
 
 G_layout = nx.shell_layout(G, nlist = [range(5, 10), range(5)], rotate = 0.)